1. Field of the Invention
The present invention relates to an image pickup apparatus including a variably-magnifying function which variably-magnifies an object image with a zoom lens, and the like, and a focus correcting function which corrects a focal plane displaced by the variably-magnifying function, and a storage medium storing a control program for controlling the image pickup apparatus.
2. Description of the Related Art
Conventionally, there has been widely known an image pickup apparatus provided with an imaging element, and a zooming function (variably-magnifying function) which moves a group of a plurality of lenses in an optical axis direction to variably-magnify.
In recent years, in such an image pickup apparatus, a request for a high-power variable-magnification lens has been particularly increased. Since a focal plane is widely moved in a variably-magnifying operation by using the high-power variable-magnification lens, it is desirable to cause the high-power variable-magnification lens to follow while correcting the focal plane along with the variably-magnifying operation.
Thus, an image pickup apparatus has been proposed which also maintains a focused condition after a zooming direction is reversed by correcting a difference of cam excursion data, which is induced because the zooming direction is different when a driving direction of the zooming is reversed, with a predetermined difference correction quantity corresponding to the zooming direction (for example, refer to Japanese Laid-Open Patent Publication (Kokai) No. H5-134163).
Since an f-value change of the high-power lens is large because of the variable-magnification, it is desirable to also control the exposure by the changed f-value during the variably-magnifying.
On the other hand, since the image pickup apparatus including a mechanism and a control of the above conventional example is frequently used as being carried, it is desirable that the image pickup apparatus is a small size-type, and a power saving-type.
Generally, if the high-power lens is downsized, the f-value change is enlarged. To power-save the apparatus in addition to the downsizing, it is general to lower a driving voltage of the apparatus, and to downsize a battery.
According to a technique of the above Japanese Laid-Open Patent Publication (Kokai) No. 5-134163, the image pickup apparatus is controlled to maintain the focused condition as correcting a focus even when a driving direction is reversed during the zooming. However, if a peak current flowing when the zooming is reversed is added with a driving current for the focusing, a driving current for the aperture, a driving current for a ND filter, and the like, it is difficult to achieve power saving due to the effect of a drop in the power supply voltage. As a result, it is not easy to realize the image pickup apparatus which is a small size-type, and a power saving-type.
Since there exists an exposure difference, and the like because of the focal plane change and the f-value change during the variably-magnifying operation, it has been particularly difficult to downsize and power-save the image pickup apparatus configured with the high-power variable-magnification lens.